Unfortunately there is a wide range of conditions that dogs and cats can get which may also present as symptoms of intestinal disease. Basically, any condition that causes severe irritation or inflammation of the small intestine and colon will produce these clinical signs. The followingis a list (by all means not exhaustive) of conditions that can present similarly:

Inflammatory Bowel Disease (IBD) - a common, allergy-initiated, auto-immune condition whereby inflammatorywhite blood cells (lymphocytes, plasma cells and/or eosinophils) attack the walls ofthe intestines and colon resulting in symptoms of gastroenteritis and colitis. Proteinsfrom the animal's food or proteinaceous bacterial antigens are thought to be the underlying cause.Whipworm - Whipworms (Trichuris vulpis) live in the colon, sometimes producingsigns of colitis.Intestinal worms - Round worms, hook worms and tape worms live in the small intestinesof dogs and cats, sometimes producing symptoms of gastroenteritis in young animals (weight loss, diarrhoea, wasting).Bacterial overgrowth - certain species of bacteria (especially Clostridium and E. coli species)live in the intestines all of the time without causing any disease issues. They normally only become a problem when their numbers are permitted to grow out of control. This generally occurs when the animal is allowed to gorge itself on rich foods (e.g. lamb and pork are huge culprits) or ingest fouled garbage (stuff from thebin, semi-rotten, spoiled foodstuffs, animal carcasses).Bacterial pathogens Some bacterial organisms preferentially invade the intestines and colon,causing signs of gastroenteritis. These include: Salmonella, Yersinia, Campylobacter and Clostridium. These organisms infect dogs and cats through the consumption of another animal's faeces or through the consumption of old/aged, undercooked or contaminated foodstuffs (e.g. food poisoning). Giardia and Cryptosporidium. - semi-common, fecally-ingested protozoan organisms that can producea range of intestinal symptoms. The organisms usually come from contaminated waterways.Viral enteric diseases. nasty intestinal viruses such as canine parvovirus, feline panleukopenia, canine distemper, canine coronavirus and rotavirus can produce symptomssevere gastroenteritis: vomiting, diarrhoea, weightloss, abdominal pain, dehydration, bloody stools etc. Diet changes - abrupt diet alterations, particularly in young animals, can commonlyproduce symptoms of gastrointestinal upset - vomiting, diarrhoea, inappetence etc.Intussusceptions - the intestine of some animals can telescope insideof itself, producing symptoms of straining to defecate, blood in the stools, vomiting, inappetence,weightloss and slimy droppings. Diagnosis is made by ultrasound, colonoscopy or exploratory surgery.Constipation - constipated animals can present with signs of straining, bloody discharges from the rectum and anus and slimy, jelly-like anal discharges.Intestinal masses - animals with intestinal, colon, rectum and anal cancers can present with signs of diarrhea, weight loss, straining to defecate, bloody discharges from the rectum and slimy, jelly-like anal discharges.Intestinal foreign bodies - animals with intestinal, colon, rectum and anal foreign bodies can present with signs of vomiting, inappetence, weight loss, straining,bloody discharges from the rectum and slimy, jelly-like anal discharges. Common foreign bodies include cooked bones, corn cobs, stone-fruit pits and pieces ofingested stick.